KR20010066830A - Light diffusion film and method using the same - Google Patents

Abstract

PURPOSE: To provide a light diffusing film which can be easily and stably produced, which has excellent light-diffusing performance, and which can improve the luminance from a light source, especially, when the film is used with a prism sheet. CONSTITUTION: A light-diffusing film 1 is obtd. by forming a light-diffusing layer 3 on at least one surface of a transparent base body 2, and the light- diffusing layer 3 consists of an ionizing radiation-hardening resin which does not contain light-diffusing particles but bas fine recesses and projections on its surface. The light-diffusing layer 3 is formed to have 1 to 10 μm 10-point average roughness and 5 to 20deg. average inclination angle θa of the recesses and projections.

Description

LIGHT DIFFUSION FILM AND METHOD USING THE SAME}

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a light diffusing film, and more particularly, to a light diffusing film having high brightness and good visibility, and a method of manufacturing the same, a surface light source, and a display device, which are used in various displays, lighting fixtures, and display panels. will be.

In various displays, lighting fixtures, or display panels, a light diffusing film for uniformly widening the light of a light source to increase visibility.

As a conventional light diffusing film, a light diffusing film and a polymethyl methacrylate resin using a film in which a light diffusing agent is dispersed in a film substrate made of a light transmissive resin such as polymethyl methacrylate resin and polycarbonate resin. And a film base material called a film base material in which a light diffusing agent is dispersed in a film base material made of a light transmissive resin such as polycarbonate resin and a light transmissive resin such as polymethyl methacrylate resin and polycarbonate resin. BACKGROUND ART Light diffusing films having irregularities formed thereon, and light diffusing films having a light diffusing layer formed by applying a composition obtained by mixing and dispersing a light diffusing agent in a light transmitting resin onto a film substrate are known.

As shown in FIG. 9, the light-diffusion film 31 is normally provided between the light guide 33 and the liquid crystal panel 34 which have scattering dots 32, and the light from the light source 35 is provided. In order to diffuse this light, many light-diffusion films have been proposed conventionally.

Moreover, in order to collect the light from a light source and to raise the brightness | luminance of the front of a liquid crystal panel, the prism sheet may be arrange | positioned between a light source and a liquid crystal panel, In this case, a prism sheet is used in combination with a light-diffusion film.

However, in the related art, the combination structure of the prism sheet and the light diffusing film is not sufficiently considered, and thus there is a problem that sufficient luminance improvement cannot be obtained by the prism sheet.

In addition, in order to solve the above problems, if a light diffusing film that matches the optical characteristics of the prism sheet is obtained, the conventional light diffusing film is difficult to manufacture, and there is also a problem that the light diffusing film cannot be stably obtained.

In addition, in the case of using the light diffusing film, it is necessary to have the light diffusing film have a function of concealing the scattering dot of the light guide plate.

The present invention has been made in view of such a point, and can be manufactured easily and stably, and further has excellent light diffusing performance, and especially when used in combination with a film sheet, a light diffusing film which can improve the luminance from a light source, An object thereof is to provide a manufacturing method, a surface light source, and a display device.

1 is a schematic cross-sectional view showing the basic layer configuration of the light diffusion film of the present invention,

FIG. 2 shows a basic layer structure of the light diffusing film of the present invention, and a cross-sectional schematic view of adding a mat layer to the light diffusing film of FIG. 1;

3 is an enlarged cross-sectional schematic diagram showing the basic configuration of the light diffusing layer of the present invention;

4 is a schematic cross-sectional view showing the basic configuration of the surface light source and the display device of the present invention;

5 is a schematic view showing an example of incident light and emitted light in the light diffusing layer of the present invention;

6 is a schematic view showing an apparatus for manufacturing a light diffusing film of the present invention;

7 is a schematic view showing a method of measuring haze value and total light transmittance of a light diffusing film of the present invention;

8 is a view showing the luminance distribution of the surface light source using the light diffusion film of the present invention,

9 is a cross-sectional schematic diagram showing the prior art.

The present invention is a light diffusing film formed by laminating a light diffusing layer made of ionizing radiation curable resin on at least one surface of a transparent substrate, wherein fine unevenness is formed on the surface of the light diffusing layer, and a ten-point average roughness of the surface of the light diffusing layer ( The above object is achieved by a light diffusing film having Rz) of 1 to 10 µm and an average inclination θa of 5 to 20 degrees.

In a preferable embodiment of the present invention, the light diffusing layer does not contain light diffusing particles.

In another preferable aspect of the present invention, the haze value of the light diffusion film is 85 to 95% and the total light transmittance is configured to be 80 to 90%.

Moreover, in the preferable aspect of this invention, when the incident angle of the light with respect to a light-diffusion film is 60 degrees-80 degrees from a normal line, it is comprised so that the peak of the emission angle from a normal line may be 30 degrees-50 degrees.

In the present invention, a mat layer may be provided on the surface opposite to the surface on which the light diffusion layer of the transparent substrate is formed.

The method for manufacturing a light diffusing film according to the present invention includes a flow-type ionizing radiation curable resin on a surface of a roll plate having a fine concavo-convex shape, and simultaneously winds a transparent base material around the roll plate to transfer the transparent substrate to the ionizing radiation. And a step of rotating the roll plate while contacting the curable resin, a step of bringing the ionizing radiation curable resin into close contact with the transparent base material during the rotation of the roll plate, and a step of peeling the transparent base material from the roll plate together with the cured resin. do.

Furthermore, the present invention includes a light guide plate for emitting light incident from the side end portion from an exit surface orthogonal to the incident surface, and a light source provided at at least one end of the light guide plate, and including a light diffusion film on the exit surface of the light guide plate. It includes a surface light source.

The surface light source may further include a prism sheet on the light diffusing film.

Furthermore, the present invention includes a display device having a display panel on the surface light source.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, in the light diffusing film 1 according to the exemplary embodiment of the present invention, a light diffusing layer 3 is provided on the transparent substrate 2, and the light diffusing layer 3 is a light diffusing particle. It is made of an ionizing radiation curable resin having a fine concavo-convex shape formed on the surface thereof, and the surface of the light diffusing layer 3 has an average inclination (θa) of 10 points average roughness (Rz) of 1 to 10 µm. ) Is formed so that 5 ~ 20 °.

In addition, in this invention, as shown in FIG. 2, the mat layer 4 can be provided in the surface on the opposite side to the surface in which the light-diffusion layer 3 of the transparent base material 2 was provided as needed.

As the transparent substrate, a resin sheet having an ionizing radiation permeability and flexibility is used, and the thickness thereof is preferably in the range of about 12 to 200 μm from the light weight and thickness of the display device used. .

Preferably, the transparent base material is polyester such as polyethylene terephthalate and polyethylene naphthalate, and methacrylic acid or acrylic acid such as polymethyl methacrylate, polymethyl acrylate, polyethyl acrylate, polyethyl acrylate, etc. Polymers of esters (so-called acrylic resins), polycarbonates, triacetate, polystyrene, polypropylene, and the like are used.

In addition, it is preferable that the transparent base material be subjected to an easy adhesion treatment such as corona discharge treatment on the surface as necessary.

The light diffusion layer has a thickness of about 10 to 200 mu m, most preferably 10 to 30 mu m, and the ionizing radiation curable resin is preferably formed into a transparent substrate as the material for forming the light diffusion layer.

As the ionizing radiation curable resin, preferably a composition obtained by appropriately mixing prepolymers, oligomers and / or monomers having a polymerizable unsaturated bond or an epoxy group in a molecule can be used. Examples of the prepolymers and oligomers include unsaturated polyesters such as condensates of unsaturated zalphonic acid and polyhydric alcohols, methacrylates such as epoxy resins, polyester methacrylates, and polyether methacrylates, and polyester acrylates. And acrylates such as epoxy acrylate, urethane acrylate, polyether acrylate, polyol acrylate and melamine acrylate.

As the monomer, Preferably styrene, -Styrene monomers such as methyl styrene, acrylic acid esters such as 2-ethylmethylhexyl acrylate, methoxyethyl acrylate and butyl acrylate, methyl methacrylate, ethyl methacrylate, methoxyethyl methacrylate and ethoxy methacrylate Methacrylic acid esters such as methyl, Substituted amino alcohol esters of unsaturated acids such as 2- (N, N-zimethylamino) ethyl acrylate, Unsaturated carboxylic acid amide such as acrylamide, methacrylamide, and geopropylene Polyfunctional compounds, such as glycol acrylate, ethylene glycol acrylate, propylene glycol gemethacrylate, and giethylene glycol gemethacrylate, vinylpyrrolidone and / or polythiol compound which has two or more thiol groups in a molecule | numerator, for example Trimetholpropane trithio acrylate, trimetholpropane trithiopropylate, betaerythritol tetrathioglycol and the like are used.

Further, when the ionizing radiation curable resin is used as an ultraviolet curable resin, among these, as a photopolymerizable agent, preferably acetphenones, benzophenones, Michler's benzoyl benzoate, N-butylamine, triethylamine, tri-n-butylhosphene, or the like can be used as the aminoxime ester, thioxetones and / or photosensitizers.

Preferably the thickness of a mat layer is about 1-100 micrometers, Most preferably, it is 5-10 micrometers, The translucent resin which disperse | distributed resin particle is used as a material for formation of a mat layer.

As the translucent resin, Preferably, polyester resin, acrylic resin, polystyrene resin, polyvinyl chloride resin, polyethylene resin, polypropylene resin, polyurethane resin, polyamide resin, epoxy resin, cellulose Woods resin, alkanoxy siloxane resin, polyimide resin, polycellophane resin, polyarylate resin and the like can be used.

Of these, polyester resins are particularly preferred from the viewpoints of controllability of refractive index differences from acrylic particles, adhesion to oily and transparent substrates, scratch resistance, light resistance and transparency of the resin itself. Do.

As the resin particles, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, polypropyl methacrylate, polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, polypropyl acryl Polymers of methacrylic acid or acrylic acid esters (so-called acrylic resins), polystyrene, polyvinyl toluene, poly- Resin particles, such as polymers of aromatic vinyl monomers, such as methylstyrene and polyhalogenated styrene, and crosslinkable monomeric polymers, such as polyaryl methacrylate and polytriaryl cyanurate, can be used.

The particle diameter is preferably 1-50 µm in average diameter, more preferably 3-50 µm, and these resin particles may be used alone or in combination of two or more thereof. In addition, you may add a light stabilizer, a heat stabilizer, an antistatic agent, and other additives suitably to a mat layer as needed.

In the light diffusing film according to the embodiment of the present invention, a light diffusing layer is provided on a transparent substrate, and the light diffusing layer is formed of an ionizing radiation curable resin in which a fine uneven shape is formed on the surface thereof. The surface of the light diffusing layer is a light diffusing film which is formed so that the 10-point average roughness Rz is 1 to 10 µm and the average inclination? 3 shows an enlarged cross-sectional view of the light diffusion layer, and FIG. 5 shows fine unevenness on the surface of the light diffusion layer.

In the light diffusing layer of the present invention, light diffusing can be performed with good efficiency. Therefore, when the light diffusing particles are included in the light diffusing layer, substances having different refractive indices are mixed and the loss of light becomes large.

In addition, if the 10-point average roughness (Rz) is less than 1 µm, light diffusion becomes weak and the concealability of the scattering dot of the light guide plate is impaired. On the other hand, if the 10-point average roughness (Rz) is larger than 10 µm, the light diffusivity is This is not preferable because it becomes strong and the front luminance is lowered.

Furthermore, if the average inclination θa is less than 5 °, the light diffusivity is weakened and the concealability of the scattering dot of the light guide plate is impaired. On the other hand, if the average inclination θa is larger than 20 °, the light diffusion is strongly It is not preferable because the front luminance becomes too low.

Here, the ten-point average roughness (Rz) is a measured value based on JISB0601-1994, which is 5 from the average value and the highest depth from the highest to the fifth to the average line of the portion where the reference length is selected from the cross-sectional curve of the measured object. This is the difference from the average value of the elevation of the floor depth to the first.

In addition, the average inclination θa is obtained by the same measurement method as that obtained when the ten-point average roughness Rz is obtained, and the average inclination of the average value between the average line and the cross section curve of the portion where the reference length is selected from the cross-section curve of the object to be measured. Value.

Hereinafter, embodiments of the surface light source and the display device using the light diffusing film as described above will be described.

As shown in Fig. 4, the surface light source 20 has a light guide body 22A having a planar light emitting surface 22A, a light emitting surface 22A of the light guide body 22, and a side opposite to the unit lens 23. A lens film 10 disposed in parallel with the plane of the lens film, the light diffusing film 9 interposed between the lens film 10 and the light emitting surface 22A, and one end surface of the light guide 22 A light source lamp 26 for injecting light into the light guide 22 from 22B, and the light incident from one end 22B is emitted from the light emitting surface 22A in the direction of the lens film 10, for example, FIG. In 4, the liquid crystal panel 28 disposed above the lens film 10 is illuminated from the rear thereof, and together with the liquid crystal panel 28, the liquid crystal display device 30 is constituted.

In FIG. 4, reference numeral 22C denotes a scattering dot provided on the rear surface (lower surface) opposite to the light emitting surface 22A of the light guide 22, and reference numeral 29 is disposed covering the bottom of the light guide 22 in FIG. Reflecting sheets for reflecting light emitted downward from the light guide 22 and returning to the light guide 22 are respectively shown.

In addition, although the lens film 10 is used as the surface light source 20 of FIG. 4, you do not need to use this lens film as needed, and you may use two lens films further. In this case, the two lens films are preferably arranged in a direction in which the ridge lines of the unit lenses cross each other.

In the present invention, when the incident angle of light to the light diffusing film is 60 ° to 80 °, the exit angle of the light from the light diffusing film is 30 ° to 50 °, and light is incident on the prism sheet. After that, the light is focused to be smaller by the prism sheet, so that the luminance of the light emitted from the prism sheet to the liquid crystal panel can be increased. In FIG. 5, as an example, the case of an incident angle of 60 degrees and an exit angle of 30 degrees is shown.

In addition, since the haze value of the light-diffusion film is 80% or more, when viewed from the liquid crystal panel side, the scattering dots of the light guide plate can be reliably hidden by the light-diffusion film.

Hereinafter, a method of manufacturing the light diffusing film as described above will be described with reference to FIG. 6.

The light diffusing film manufacturing apparatus 90 for implementing this manufacturing method uses a roll plate 94 on which the fine unevenness is formed to form a light diffusion layer on the surface of the transparent base material 12 wound on the roll plate 94. Application and curing.

More specifically, the fine concave-convex portion 92 is a liquid UV curable resin 96 from the coating device 98 disposed in contact with the circumference of the roll plate 94 below the roll plate 94. Continuously supplied (coated) to the concave-convex portion 92, and the concave-convex portion (on the inner surface of the transparent base material 12) wound by the inlet and outlet side guide rolls 91A and 91B on the roll plate 94 The transparent substrate 12 is irradiated with a predetermined amount of ultraviolet rays to the ultraviolet curable resin 96 of the fine uneven portion 92 with the transparent substrate 12 in the middle by the ultraviolet irradiation device 100 while contacting the resin of 92. Cured in the state attached to).

In order to faithfully follow the shape of the fine concavo-convex portion 92, the liquid ultraviolet curable resin 96 preferably has a viscosity of 5000 cps or less, particularly 1000 cps or less.

When the transparent substrate 12 is separated from the roll plate 94 along the exit side guide roll 91B in a state where the resin 96 is bonded to the transparent substrate 12, the cured resin 96 is formed with fine uneven portions ( 92).

Thereafter, if necessary, the mat layer may be laminated as described above.

According to this manufacturing method, since resin can be formed according to the shape of the roll uneven plate designed previously, the fine unevenness | corrugation of a desired shape can be faithfully reproduced. Therefore, one having a predetermined diffusion characteristic can be manufactured with high accuracy, and it is difficult to cause disturbance due to a place in the screen. In addition, coating stains, which are easy to occur in the conventional light diffusing film, are less likely to occur.

Moreover, since the fine concavo-convex is formed by the roto-convex plate using the roll concave-convex plate while traveling the sheet substrate of the strip-shaped web, the molding is also immediately cured by ionizing radiation, thereby making it possible to manufacture continuously and at low cost.

Example

Hereinafter, the present invention will be described in detail with reference to Examples.

Example 1

As a transparent substrate, a 125 μm-thick polyethylene naphthalate film (A4300: product name, manufactured by Dongyang Bang Co., Ltd.) was used, and an ultraviolet curable resin (Seikabeam XD-808: product name, Daeil Chemical Co., Ltd.) was used as a light diffusion layer thereon. Production), and a light diffusing layer having a thickness of approximately 20 µm was formed by the method of manufacturing the light diffusion sheet. After that, 200 parts by weight of a polyester resin (Byron 200: Samgye Co., Ltd., Tong Yang Bang Co., Ltd.), resin particles (micro silica aerosol OK412: trade name, manufactured by Nippon Aerosol Co., Ltd.) An average particle diameter of 4 µm) 3 parts by weight, toluene 20 parts by weight, MEK 20 parts by weight, a coating liquid consisting of a curing agent (XEL Curing Agent: trade name, manufactured by Inktec Co., Ltd.) is applied, dried, and a mat having a thickness of approximately 5 µm. A layer was formed to form a diffusion layer film.

As Comparative Examples 1 and 2, a light diffusing layer in which light diffusing particles were dispersed in a light transmissive resin was formed on a transparent base film, and a commercial light diffusing film having irregularities formed on the surface of the light diffusing layer was used. . Each light diffusing film is Comparative Example 1 (trade name; D121, manufactured by Dec. Electric Co.) and Comparative Example 2 (trade name; BS-01, manufactured by Hyehwa Corporation).

These are light-diffusion films which show haze values and total light transmittances as shown in Table 1, and have irregularities on the surface of the light diffusing layer as shown in Table 2 below.

Table 1

Total light transmittance (%) Haze Example 1 83.5 89.9 Comparative Example 1 70.6 90.9 Comparative Example 2 73.2 88.5

TABLE 2

10-point average roughness Rz (㎛) Average slope θa (deg) Example 1 7.49 13.2 Comparative Example 1 19.48 21.5 Comparative Example 2 12.36 20.9

In addition, the haze value is as shown in FIG. 7 by a haze meter manufactured by Dongyang Period, to hold the light diffusing film 101 of the example or the comparative example to the jig 102 and to the light source 103 from the front. Irradiated light was received by the light-receiving portion 104 from the front surface and measured, and the total light transmittance was also measured.

Surface roughness was measured by the surface roughness measurement system subcoder SE-30K of the platelet laboratory with a measuring length of 2.5 mm, a measuring speed of 0.1 mm / sec, a measuring force of 0.7 mN, and a tip diameter of 2 占 퐉.

When the light diffusing film produced in Example 1 was irradiated with light at an incident angle of 80 °, the light exit angle was 40 °.

The light diffusing film was assembled into a surface light source 20 having a structure as shown in FIG. 4 and used, resulting in a luminance distribution of the surface light source as shown in FIG. EZContrast16R manufactured by ELDIM was used for luminance distribution measurement.

As shown in FIG. 8, it can be seen that in Example 1 of the present invention, the luminance is clearly improved at a viewing angle of 10 ° to 30 ° with respect to the comparative example.

The light diffusing film, the manufacturing method, the surface light source and the display device according to the present invention can be manufactured easily and stably, and further, the light diffusing performance is excellent, and especially when used in combination with a film sheet to improve the brightness from the light source. It can be effective.

Claims (10)

A light diffusing film formed by laminating a light diffusing layer of ionizing radiation curable resin on at least one surface of a transparent substrate, the light diffusing layer having fine irregularities on the surface thereof, and having a ten-point average roughness (Rz) of the surface of the light diffusing layer being 1 Light diffusion film, characterized in that the average inclination (θa) is 5 ~ 20 ° and ~ 10㎛. The light diffusing film of claim 1, wherein the light diffusing layer is essentially free of light diffusing particles. The light diffusing film of claim 1, wherein the light diffusing film is configured to have a haze value of 85 to 95% and a total light transmittance of 80 to 90%. The light diffusing film of claim 1, wherein the peak of the exit angle from the normal line is 30 ° to 50 ° when the incident angle of light to the light diffusing film is 60 ° to 80 ° from the normal line. The light diffusing film of claim 1, further comprising a mat layer on a surface opposite to a surface on which the light diffusing layer is formed. On one side of the transparent substrate, a light diffusion layer of ionizing radiation curable resin having fine irregularities, 10-point average roughness (Rz) on the surface of 1 to 10 µm, and an average inclination (θa) of 5 to 20 ° is laminated. As a manufacturing method of a light diffusing film made of, Applying a flow-type ionizing radiation curable resin to the surface of the roll plate on which the fine irregularities are formed, and winding the transparent substrate around the roll plate to rotate the roll substrate while contacting the transparent substrate with the ionizing radiation curable resin; And a step of bringing the ionizing radiation curable resin into close contact with the transparent base material during rotation of the roll plate, and a step of peeling the transparent base material from the roll plate together with the cured resin. The method of manufacturing a light diffusing film according to claim 6, wherein each of the steps is performed continuously. The light guide plate which emits the light incident from the side end part from the exit surface orthogonal to the incidence surface, and the light source provided in at least one edge part of the light guide plate, Comprising the light-diffusion film of Claim 1 on the exit surface of the light guide plate Surface light source characterized by the above-mentioned. The surface light source of claim 8, further comprising a prism sheet on the light diffusing film. A display device comprising a display panel on the surface light source according to claim 8.